Apparatus for driving machines.



B. GRAEMIGER.

APPARATUS FOR DRIVING MACHINES.

APPLICATION FILED MAY 5, 1914.

Patented July 17, 1917.

Specification of Letters Patent.

* Patented July 17, 1917.

Application filed May 5, 1914. Serial No. 836.491.

To all whom it may concern:

Be it known that I, BENJAMIN GRAE- NIGER, a citizen of the Republic ofSwitzerland, residing at 19 Hardturmstrasse, Zurich, Switzerland, haveinvented new and useful Improvements in Apparatus for Driving Machines;and I do hereby declare the following to be a full, clear, and exactdescription of the invention, such as will enable others skilled in theart to which it appertains to make and use the same, reference being hadto the accompanying drawing, and to letters or figures of referencemarked thereon, which form a part of this specification.

This invention relates to apparatus for driving machines, whereinelectro-dynamic or purely magnetic forces are used and the driving anddriven members are separated from each other in a gas tight mannerwithout the provision of'a stufling box by a partition or wall.According to the invention a metal alloy of great strength and which isa very bad electrical conductor is employed for the separating partitionbetween the driving and driven members. The invention consistsparticularly in the use of a special steel, which is a very badelectrical conductor.

A power driven machine inclosed in a casing can be driven for instance,from the exterior without involving the use of a stufling box byinclosing the rotor of an electromotor of any suitable constructioncoupled to the shaft of said machine in .said casing and by separatingthe driving member, that is to say the stator of the motor in a gastight manner from the rotor by a wall or partition forming a part of thecasing. In order that the efficiency of the motor may be as high aspossible notwithstanding the partition wall between the rotor and thestator the material to be used for such partitions must fulfil thefollowing main requirement:

The material must have an electric resistance as high as possible inorder to minimize the currents set up in the wall and the consequentlosses. There is further to choose between materials which aremagnetizable of the same size, not

current must then be increased as compared tain output the motor has tobe made of a largensize than would be the case if the conditions werenormal. Besides the efficiency is impaired, and in a three-phase m0- toralso the power-factor will be smaller.

On the other hand, if a magnetizable metal isused, the magnetic leakageor dispersion 1n the stator is facilitated, so that also inthis instancean increase of the magnetlzatlou current will take place. The resultsare in general the same as in the case, when a nonmagnetizable metal isused. It has been found that under the same circumstances (samethickness of the wall and same electrical resistance) the efiiciency andthe power-factor will not vary very much if non-magnetizable walls areused instead of magnetizable ones, and in order to ascertain which metalis used with best advantage, every single case has to be consideredseparately.

If the metal alloy of high ohmic resistance is magnetizable, it ispreferable to provide also between the partition wall and the stator-boxa small air-gap. The leakage is then made more diflicult.

In all cases, however, the metal must be of great strength so that thepartition wall can be made thin and thus avoid unduly increasing of thedistance between the rotor and the stator by the interposed partition ascompared with arrangements where a motor fitted with a separatingpartition is employed. Besides this, the eddy-current losses and thelosses through the short circuiting of the lines of forces will be theless the thinner the partition.

lVith a view to insuring a gas-tight joint of the partition with therest of the casing it is advantageous to employ a metal capable of beingbrazed or welded.

All these combined requirements are best fulfilled according to thisinvention by using as the material for the separating wall a metal alloyhaving great strength and which is a very bad conductor of electricity.Certain special steels are particularly well adapted for being employedfor such walls.

An alternative method of driving a machine inclosed in a casing Withoutthe use of a stufiing box consists in employing an electro dynamic orpurely a magnetic clutch of any suitable construction, wherein theperipherally acting force required for transmitting the motive power oroutput is provided by the magnetic flux lines between the two clutchelements without contact between such elements, so that therefore one.of the clutch elements can be inclosed in the casing with the machineto be driven, while the other clutch element, driven by a motor of anykind, is arranged outside the casing. The separating partition betweenthe two clutch elements and which forms part of the casing must becapable of fulfilling the same requirements as in the former case, thatis tosay, where an electro-motor is used,

since also in this case there has to be avoided as far as possible theformation of eddycurrents in the partition and there has to be reducedto a minimum the distance of gap between the two clutch members in orderto hold the number of ampere-windings necessary for the excitation ofthe magnet as small as possible and to minimize the loss in the outputdue to such gap.

It has been found that it is much better to employ in magnetic clutchesnon-magnetizable partitions, since much better 'results will then beobtained. According to the present invention the partition will be madealso in this instance preferably of a metal alloy, Whichis a very badconductor of electricity. In all cases the main feature of thisinvention consists in employing a metal alloy for the separating wallhaving a high ohmic resistance. This is con-' trary to all that whichhas been previously proposed. Hitherto, it was the general be- .lief,that only non-conductors (ebonite or fiber) could be employed for suchpartition walls or alloys of low ohmic'resistance, e. 9., goodelectrical conductors. It is a fact that in employing materialselectrically non-conducting, eddy-currents are entirely eliminated. Butif such walls should have the desired strength and density, it isnecessary to make them of such a thickness, that such arrangements ofdriving apparatus, either in the form of a motor or a clutch couldhardly be carried out owing to the great distance between the drivingand driven members. It is moreover very diflicult to connect permanentlyin a ,fiuid tight manner a partition wall made of a non-metal to'netizable. Further, high per cent. nickelsteel and silicon-steel with5% silicon may also be employed, for such partition walls.

Some of these alloys have an electrical resistance which is nearly ahundred times greater than that of the copper, and the theory and thepractice have shown, that this is more thansuflicient to minimize thelosses due to eddy-currents to such an extent that they cannot be ofgreat harm.

Driving arrangements embodying this invention are specially adapted forinstance for driving the compressor of an ice or refrigerating machine,such compressor being entirely inclosed in a casing forming the deliveryor suction chamber. In this way all need for the use of a stufiing-boxwhich would be in communication on one side with the atmosphere, isobviated and thus the loss of the working fluid or the entrance of airin said chamberi's rendered impossible.

Two examples of apparatus according to the invention are illustrated inthe accompanying drawing.

Figure 1 is a vertical section of a threephase motor.

Fig. 2 is an enlarged .detail section at right-angles to the axis of themotor.

.Fig. 3 is a vertical section of an electromagnetic clutch, and

Fig. 4 is a transverse section taken on line III of Fig. 3.

Fitted within the central boring in the stator s of the motor is asleeve h made of a non-magnetic metal alloy of great strength and whichis a bad conductor of electricity. This sleeve is connected to thestator s at A by brazing, so as to form a gas-tight joint, and asimilarjoint is made at B between the stator and the casing g.

The rotor 1', which in this example is constructed in the form of ashort circuited armature, is keyed to the shaft w, of the machine to bedriven, said shaft being supported in a bearing L, formed in the casingg which incloses said machine. The sleeve h when magnetic will not bearranged with a close fit within said boring of the stator s, but willbe preferably arranged in such a manner that a small clearance is leftbetween'the sleeve and the stator to reduce the magnetic dispersion.This is clearly shown in Fig. 2 drawn on a larger scale. This figureshows a sectionat right angles to the axis of the motor through thestator metallic parts takes place between the stator.

s and the sleeve h. The clearance provided between these parts may befilled up by a paper-layer, a coating or the like.

Figs. 3 and 4 illustrate an example for an arrangement wherein thedriving and the driven members of an electro-magnetic clutch areseparated from each other in a gas-tight manner, that is to say, a casewhere purely magnetic action is employed for transmitting power. On theshaft 6, driven by a prime mover or machine of any kind, is keyed thedriving member, of the clutch, consisting of two disks in and m betweenwhich is arranged the winding 0 required for excitation pur oses. Thetwo disks 1: and we have cylin rical polar surfaces arranged facing eachother and formed with projections 7 and 8 respectively. The drivenclutch member is keyed on the shaft 0 of the machine to be driven andconsists of a bell shaped disk n, the cylindrical portion of whichextends between the two polar surfaces of the driving clutch member andis also formed with projections 9 on the inside and projections 10 onthe outside. The separating partition p arranged between the two clutchmembers is in the form of a ring of U-section and is connected in agas-tight manner to the parts 9 and t of the casing. The action of theclutch is due to the fact that the magnetic flux lines, generated by theenergizing winding, set up, in passing from the polar projections 7 and8 of the driving clutch member to the polar projections 9 and 10 of thedriven clutch member, (there being a certain amount of angulardisplacement between the said polar projection), a component of force ina peripheral direction, see Fig. 4., which is a part vertical sectioncorrespondin to the line III at right angles to the axls of the clutch.In ac= cordance with the invention a non-magnetic metal alloy of greatstrength and having as high an ohmic resistance as possible is employedfor the separating partition ;0. In this arrangement it is better to usea nonmagnetizable alloy instead of a magnetizable one.

The subject matter of the present invention, that is, the partition wallconsisting of a metal alloy having a very high ohmic resistance, may beemployed in connection and great strength.

with every kind of electromotors, electrodynamic and magnetic clutches.

Having now particularly described and ascertained the nature of my saidinvention and in what manner the same is to be performed, I declare thatwhat I claim is:

1. In an apparatus for driving a machine by means of electro-dynamic orpurely magnetic action, a driving member, a driven member, and apartition wall separating said members from each other in a gas-tightmanner, said wall being constructed of a metal alloy having a very highohmic resistance and great strength.

2. In an apparatus for driving a machine by means of electro-dynamic orpurely magnetic action, a driving member, a driven member, and apartition wall separating said members from each other in a gas-tightmanner, said wall being constructed of a practically non-magnetizablemetal alloy having a very high ohmic resistance and a great strength.

3. In an apparatus for driving a machine by meansof electro-dynamic orpurely magnetic action, a driving member, a driven member and apartition wall separating said members from each other in a gas-tightmanner, said wall being constructed of a steel alloy having a very highohmic resistance.

4:. In a device for driving a machine by means of an electromotorincluding a stator, a rotor, and a partition wall separating said rotorand stator and inclosing said rotor from the stator in a gas-tightmanner, said partition wall being constructed of a metal alloy having avery high ohmic resistance 5. In a device for drivin a machine by meansof an electromotor inc uding a stator, a rotor and a partition wallseparating said rotor and stator and inclosing said rotor from thestator in a gas-tight manner, the improvement which consists inconstructing said partition wall of a non-ma etizable metal alloy of ahigh per cent. nlckel steel having a very high ohmic resistance andgreat strength.

In testimony that I claim the foregoing as my invention, I have signedmy name in presence of two subscribing witnesses.

' BENJAMIN GRAEMIGER.

